Sept 19 (Reuters) - U.S. investment bank Jefferies Group LLC’s third-quarter profit more than doubled as it earned more from advising on debt and equity offerings as well as mergers and acquisitions.

New York-based Jefferies, a unit of Leucadia National Corp , traditionally kicks off the earnings reporting season for investment banks. Its results are viewed as an indicator of big Wall Street banks’ performance.

Despite posting record net revenue for the quarter, Jefferies’ trading revenue fell a 7 percent, hurt by lower volatility during much of the quarter.

JPMorgan Chase & Co, Bank of America Corp and Goldman Sachs Group Inc have already warned that trading conditions during the third quarter will likely be poor as bonds and stocks continue to suffer from decreased market activity and volatility.

JPMorgan has said it expects a 20 percent slide in trading revenue, while BofA and Citi expect a nearly 15 percent fall.

Jefferies said revenue from investment banking, which includes underwriting and advisory services, soared 61 percent to $475.7 million.

In the quarter, Jefferies provided debt financing to Sycamore Partners’ $6.9 billion deal to buy Staples Inc . U.S. oil and gas company Penn Virginia Corp also hired Jefferies as it explored a possible sale.